I would look at the inverter type heat pump (same as a mini split), with a gas backup. The new heat pumps will work down to -25 degrees, although we have ours set to switch to gas for heat at 15 degree outside temp.
  In my motel I have only mini splits, they work really good down to -5, (they are older units) at -10 and a high wind for several days, they will keep it at 65 degrees, but struggle to go above that. We have those conditions maybe once every 3-5 years.